A bomb exploded Monday near a mass political rally where thousands of supporters of Nepal's main political parties had gathered to mark the start of campaigning for elections, police said. No one was killed, but five people were wounded in the blast, police official Uma Chaturbedi said. Police were interviewing witnesses who saw someone toss the bomb out of a car and into the crowd as it was breaking up. No one has claimed responsibility. To mark the start of the election campaign, 50,000 people - supporters of the seven political parties in the ruling coalition, including former communist rebels widely known as Maoists - marched through Katmandu and gathered at the rally grounds in the heart of city.